The present invention relates to aircraft and aircraft wings, and more particularly to aircraft with wings for receiving a wing tip comprising a fuel pod, and to methods of designing such wings.
It has been recognised that it may be desirable for aircraft to be able to efficiently operate over a variety of different mission profiles. For example, it may be desirable for an airline to be able to operate a passenger aircraft over a first mission profile having a short range for part of a year (for example the summer), but to also be able to operate the aircraft over a second mission profile having a medium (i.e. longer) range for another part of the year (for example the winter).
To increase the range of an aircraft it is usually necessary to increase the fuel capacity.
It is known to provide fuel capacity by locating permanent fuel pods on aircraft wing tips. For example GB 1087784 discloses an aircraft having wing tip pods. Furthermore the Nimrod MRA4, the B-45 Tornado, Lockheed Super Constellation and Learjets 23 and 24 all have fuel pods at the wing tips. In these above-mentioned aircraft, the wings are designed specifically for performance with the fuel pod fitted. Where the extra capacity of the fuel pod is not required (e.g. for shorter range mission profiles) the aircraft performance is sub-optimal because there remains a drag and weight penalty from the fuel pod, and unnecessary structural margins in the wing. This restricts the commercial feasibility of regularly running an aircraft with permanent wing tip fuel pods, over a range of different mission profiles.
Some military aircraft have single-use fuel pods (often referred to as ‘drop tanks’) that are mounted on the wing tips and can be jettisoned after use. U.S. Pat. No. 2,575,534 describes an aircraft having a ‘drop tank’. These fuel pods can be used to extend the range of an aircraft for particular mission profiles, but are unsuitable for use on commercial passenger aircraft. Furthermore, the wings of such aircraft are typically designed for use without the drop tank, and therefore have relatively poor performance with the tank fitted. This restricts the commercial feasibility of regularly running an aircraft with such wing tip fuel pods fitted.
It is desirable to provide an aircraft that can more efficiently operate over a variety of different mission profiles.